Optimization experiments were performed in CHO-K1 cells. Cells (2 x 104) were seeded in quadruplicate into 96-well plates and transfected 24 hours later with an in vitro-transcribed CAT-encoding RNA using [A] increasing amounts of RNA with 1.5 µl TransMessenger Reagent and [B] increasing amounts of TransMessenger Reagent with 0.25 µg RNA, as described in the TransMessenger Transfection Reagent Handbook. CAT activity was measured 24 hours post-transfection.